The invention relates to a beam splitter for electron beam machines with a beam splitter grid which is to be set crossways to the beam and which has a row of crosspieces running next to one another with uniform spaces for shading the portions of beam striking it.
With the electron beam perforation of synthetic material, especially artificial leather, it is advantageous if work is carried out simultaneously with several individual beams. It is well known to subdivide an electron beam of relatively large cross-section by means of beam splitters; these beam splitters consist, in the simplest case, of sheets with a corresponding amount of holes. Generally, such beam splitters can be formed so that they consist of a number of cross-pieces, which shade the beams, and of a number of free spaces lying between the cross-pieces, through which corresponding amounts of the beam can penetrate. For mass perforation with a high work speed, it is especially practical to produce a line beam, to focuus this into a line-shaped focal spot on the place of work, and to set up a beam splitter in front of the place of work which subdivides the line beam into a quantity of individual beams with a roughly punctiform cross-section. With the high work speeds that material to be perforated is mostly moved continuously through the place of work, and the beam being deflected during the perforation impulse corresponding to the speed of movement of the material, the spaces between the cross-pieces are to be formed long enough to permit laterial beam movement.
The cross-pieces are heated so much by the beam portions striking them, that the danger of melting exists even with the use of a high melting point material such as tungsten. Moreover, the cross-pieces are contaminated by the waste-products collected during working. The relatively high temperature of the cross-pieces admittedlyy provides for a certain automatic cleaning; nevertheless, after a certain time, which for perforating synthetic products can total only minutes, so much material has been deposited on the cross-pieces that the required division geometry is no longer present. Such difficulties make numerous interruptions to work necessary which are troublesome and time-consuming on account of the vacuum necessary in the work chamber. For this reason, use has frequently not been made of the beam splitter.